Effects of Vitiated Air on Hydrogen Ignition in a High-Speed Laminar Mixing Layer

Authors: B. Han, C. J. Sung, and M. Nishioka

Direct link to the paper: DOI:10.1080/00102200490256018

Abstract:

One associated complication for the use of vitiatedair in laboratory supersonic combustion studies to simulate flight enthalpy is that the test media are contaminated by species that are not representative of the actual atmosphere. When burning hydrogen in oxygen-enriched air is employed to produce vitiatedair in experimentation, the resulting high-enthalpy airflow contains substantial amounts of, for example, H2O, H, OH, O, and NO. Therefore, the primary objective of the present numerical study is to assess the effects of vitiatedair on the ignition characteristics in supersonic experiments. Specifically, the ignition evolution in the high-speedhydrogen/airlaminarmixinglayer is computationally simulated using detailed chemistry and transport properties. Individual and combined influences of important contaminants on ignition are systematically examined over a range of pressure, air temperature, and freestream velocity variations. Vitiations of the active radicals, like H, O, and OH, are found to enhance ignition, as expected. Results also show that contamination of H2O and NO can inhibit and promote supersonic ignition, respectively. The computed results on the net effect of simultaneous contaminations of H, O, OH, H2O, and NO on the ignition response further provide insight into the interpretation of the experimental data using the vitiatedair facilities.